From 3ce3820553ddaf709d4a6aab50556ac619f5ba2f Mon Sep 17 00:00:00 2001
From: lassulus <lassulus@lassul.us>
Date: Sat, 23 Jan 2021 20:44:52 +0100
Subject: l: init ecrypt

---
 lass/5pkgs/ecrypt/default.nix | 108 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 lass/5pkgs/ecrypt/default.nix

diff --git a/lass/5pkgs/ecrypt/default.nix b/lass/5pkgs/ecrypt/default.nix
new file mode 100644
index 000000000..9bb35a8dc
--- /dev/null
+++ b/lass/5pkgs/ecrypt/default.nix
@@ -0,0 +1,108 @@
+{ pkgs, lib }:
+
+#usage: ecrypt mount /var/crypted /var/unencrypted
+pkgs.writers.writeDashBin "ecrypt" ''
+  set -euf
+  set -x
+
+  PATH=${lib.makeBinPath (with pkgs; [
+    coreutils
+    ecryptfs
+    gnused
+    gnugrep
+    jq
+    mount
+    keyutils
+    umount
+  ])}
+
+  # turn echo back on if killed
+  trap 'stty echo' INT
+
+  case "$1" in
+    init)
+      shift
+      mkdir -p "$1" "$2"
+
+      # abort if src or dest are not empty
+      if [ -e "$1"/.cfg.json ]; then
+        echo 'source dir is already configured, aborting'
+        exit 1
+      elif ls -1qA "$2" | grep -q .; then
+        echo 'destination dir is not empty, aborting'
+        exit 1
+      else
+        stty -echo
+        printf "passphrase: "
+        read  passphrase
+        stty echo
+        sig=$(echo "$passphrase" | ecryptfs-add-passphrase | grep 'Inserted auth tok' | sed 's/.*\[\(.*\)\].*/\1/')
+        mount -t ecryptfs \
+          -o ecryptfs_unlink_sigs,ecryptfs_fnek_sig="$sig",ecryptfs_key_bytes=16,ecryptfs_cipher=aes,ecryptfs_sig="$sig" \
+          "$1" "$2"
+
+        # add sig to json state file
+        jq -n --arg sig "$sig" '{ "sig": $sig }' > "$1"/.cfg.json
+      fi
+      ;;
+
+    mount)
+      shift
+      if ! [ -e "$1"/.cfg.json ]; then
+        echo '.cfg.json missing in src'
+        exit 1
+      fi
+      old_sig=$(cat "$1"/.cfg.json | jq -r .sig)
+
+      # check if key is already in keyring, otherwise add it
+      
+      if keyctl list @u | grep -q "$old_sig"; then
+        echo 'pw already saved'
+      else
+        stty -echo
+        printf "passphrase: "
+        read  passphrase
+        stty echo
+        new_sig=$(echo "$passphrase" | ecryptfs-add-passphrase | grep 'Inserted auth tok' | sed 's/.*\[\(.*\)\].*/\1/')
+
+        # check if passphrase matches sig
+        if [ "$old_sig" != "$new_sig" ]; then
+          echo 'passphrase does not match sig, bailing out'
+          new_keyid=$(keyctl list @u | grep "$new_sig" | sed 's/\([0-9]*\).*/\1/')
+          keyctl revoke "$new_keyid"
+          keyctl unlink "$new_keyid"
+          exit 1
+        fi
+      fi
+
+      sig=$old_sig
+      keyid=$(keyctl list @u | grep "$sig" | sed 's/\([0-9]*\).*/\1/')
+      if (ls -1qA "$2" | grep -q .); then
+        echo 'destination is not empty, bailing out'
+        exit 1
+      else
+        mount -i -t ecryptfs \
+          -o ecryptfs_passthrough=no,verbose=no,ecryptfs_unlink_sigs,ecryptfs_fnek_sig="$sig",ecryptfs_key_bytes=16,ecryptfs_cipher=aes,ecryptfs_sig="$sig" \
+          "$1" "$2"
+      fi
+      ;;
+
+    unmount)
+      shift
+
+      sig=$(cat "$1"/.cfg.json | jq -r .sig)
+      keyid=$(keyctl list @u | grep "$sig" | sed 's/\s*\([0-9]*\).*/\1/')
+
+      umount "$2" || :
+      keyctl revoke "$keyid"
+      keyctl unlink "$keyid"
+      ;;
+
+    *)
+      echo 'usage:
+        ecrypt init /tmp/src/ /tmp/dst/
+        ecrypt mount /tmp/src/ /tmp/dst/
+        ecrypt unmount /tmp/src/ /tmp/dst/
+      '
+  esac
+''
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